rage against the ground loop

I'm raging for two reasons.

1) My audio install is giving me absolute hell.
2) My ridiculous audio install is keeping me from enjoying my S2000 on the road.

Please help me solve this so I might cruise the roads once again.

I'm going to attempt to organize a decent amount of information into four sections.

//--- The Components ---- \\

    Car: 2001 Honda S2000
    Head Unit: Kenwood Kdc-Bt945U
    Amplifier: JL M6450 Class A/B Six-Channel (45W RMS x 6 @ 4 ohm )
    Speakers: Jl Audio C2-650 Component
    Amplifier 2&3: Boss Audio CX250 x 2 (Rated at "400watts" :rolleyes: )
    Subs: Aura Bass Shakers x 2
    TSUNMAI FBWM801-ANL Fuse Block
    TSUNMAI - Solid Distribution block x 2

//--- Installation ---- \\

Head Unit:
The head unit is currently powering the left speaker, while the JL M6450 is powering the right speaker. I never made it to the second speaker before I hit problems.

The headunit is wired up using a modify harness and everything worked as expected when stock When replacing the passenger side door I rewired everything with 16 gauge wire and simply zip tied the factory speaker harness down.

Originally I had the power line (4 Gauge) running right next to the three sets of RCA's and one set of speaker wire, but have since relocated the speaker wire and three sets of RCA's to run down the center console to get it away from the power wire. I thought this had made a difference, but it seemingly did nothing.

Where the factory spare tire was, I built an MDF platform:



NOTE: This was a mid install picture, the single distribution block shown here is where the negative block now is, and above the fuseblock is the power distribution block. None of my wires are just electrical taped together, at a minimum wires are taped, heatshrunk or crimped, taped, then heat shrunk. I did however use that 12 gauge wire to connect one of the BOSS amps and not the 4 gauge. The other boss amp is 4 gauge, the main JL amp is 4 gauge. The power wire connects to the fuseblock, then the distrobution block. The negative block is of course connected to my chassis brace bolt.

//--- The Problem ---- \\

The bass shakers work perfectly with the stock speakers. Zero distortion from either.

The stock speaker and the now amped JL speaker work perfectly without the bass shakers.

As soon as I plug in the subwoofer RCA from the head unit into one of the BOSS amps, via a splitter or going directly to a single amp I get ground loop noise out of the aforementioned bass shaker and also out of the amplified speaker. The stock speaker as expected always works in this situation.

//-- What I've Tried --- \\

My first instincts told me to get the speaker and RCA cables away from the power line. Done.

My second thought was to reinspect my common ground to the chassis. What's this? TONS of primer around the bolt hole because I was lazy? You bet. 10 minutes later with a wire wheel on a dremel the metal is peeled back and shining!

After both of those failed to even remotely help, I began a frustrating mis-match game. I tried all of the 3 RCA's in the SUB / FRONT jacks in multiple combinations, but nothing changed between them. They were purchased new, Monster Cables approx 10 ft. long I think.

After swapping the RCA cables in and out, I tried disconnecting one of the BOSS amps to see if it helped. It helped somewhat, as I recall but nothing drastic at all. With the second amp out disconnected from both power and ground it then just became like the stock speaker and amped speaker senario and it sounded fine once again.

I also tried experimenting with the ground on the head unit, I tried originally grounding it to the factory harness (Never had an issue with noise before this) and then I tried grounding it in several in-cabin places, as well as tried grounding it to the common ground in the rear, and also the battery. None of which changed the feed back loop at all.

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So, I think that does a halfway decent job as describing my problem in detail. I can provide more detail upon request.

I'm really out of ideas here.

One more thing I should mention. One possibly important thing, if I take the head unit ground, and ground it on the RCA's - BOOM. Zero distortion instantly.

I don't want, I refuse to install my system this way - if there is any other possible way I'll do it.

Thanks yall, please ask if you need more information/questions.

-Greg

This afternoon I will try swapping out the Boss amplifier for either my spare Infinity or Clarion amps which are both currently running in working installs to see if the noise is coming from the BOSS amps.

My gut still says this is a head unit problem.

I asked Kenwood tech department this question:

Does grounding the RCA's that plug into the head unit with the ground from the head unit (this cause all noise to cease) indicate a failure of the internal ground in the head unit?

I received this as an answer:

No, grounding the RCA will somehow eliminate the noise. We have this feature on some of our units.

REALLY? A "Feature"?

Somehow I doubt this response.

-Greg

Not that anyone was jumping on this, but after another couple hours of playing around I've 100% narrowed it down to two things.

Either all of my monster RCA cables are junk, or the pre-outs on the headunit are junk.

The ground wire to the RCA was in fact a band aid for a grounding problem at the RCA level.

-Greg

Have you addressed the underhood grounds? Specifically, battery-to-chassis, alternator-to-engine, and chassis-to-engine.

That's where I'd look next.

As far as your question re: Kenwood's answer. It's not BS. I've seen many components that have a switch to "lift" the ground. Nope. It's a legitimate answer.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

It's a pretty new car with lowish miles, everything is incredibly clean engine wise. I'd be disappointed if the stock engine grounds were this bad. =(

Anyway, what kind of switch to lift the ground are you talking about?

I've owned a hand full of head units, but I don't recall anything that would fit that description. I'm fairly certain my current Kenwood does not have one.

In regards to the Kenwood question: I don't believe that should ever be required if everything is working correctly. Could you explain why this would be necessary? I aim to solve this puzzle without resorting to that.

-Greg

Stock grounds are not designed to handle big amps - the engine to battery ground will (because of the high current starter motor) but not necessarily the battery to chassis/body ground.

Breaking ground is s common and legit solution to ground loops. Do a search on the subject for explanations (wiki is probably ok).

Hmm, I didn't realize my am[s were considered that big.

The JL amp is an A/B but it's still like 400watts total. The boss amps are realistically probably 100 watts if they are lucky.

While groudning RCA's manually may be a COMMON solution, I don't think it's a good one... I think that it pretty widely agreed.

I have no idea what output they are, but I assumed big since my standard HU puts out 4x45W = 180W (RMS!) and I'd expect a bigger and dedicated amp to put out way more than that. (Hence 400W + >400W = over 80A.)

The JL @ 4 ohm is 45 x 6 RMS for 270 RMS, not a ton.

I'll see if I have enough wire left over to make a new battery ground out of the 0/4 AWG gauge.


In the meantime, I need to grab some more RCA cables and find out if the cables or head unit is the issue.

Cheers,

-Greg

Disconnect the RCA cables from their respective jacks - do both ends. Using an ohmmeter set on continuity, ring out the RCA jack grounds (to ground) on the amplifiers. If they show continuity, do the same on the deck. This will tell you which end is the "funky" one. If neither end shows continuity, THAT is why touching a wire between ground and the shield kills the whine. Any resistance readings you receive SHOULD be less than one ohm. With a partner, check that resistance (from the RCA jacks) to the battery ground. Also check the resistance from the alternator housing to battery ground. It should effectively be the SAME resistance as the meter leads alone.

As to the underhood grounds... My 2001 Civic, with less than 1000 miles on it needed a complete grounding rewire when I went to put the FIRST of my systems in. Hondas are unibody cars, and most of the latest ones are all held together with adhesives, with a (relatively) bare minumum of actual spot-welds, and spot-welds SUCK for continuity, anyway... It's not a "failure" or a disappointment, per se, it's just the way they're built.

Even 270WRMS can add a significant power load to a minimally overspecified alternator. Yours will be about 55A, and that's a hot rating. 270 watts is about 25A alone, at the BEST of times. Real world will likely be a bit worse than that. That's 50% of your alternator! Add AC, lights, power windows, fans... You see where this is going, right?

We never said that grounding RCAs was a "common" solution... (well, *I* never said it that way) We said it was a "viable" (or legit) solution. :) Your deck will probably not have a ground lift switch, and it's not a bad thing if it doesn't. We'll get this for ya. :)

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote:

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Disconnect the RCA cables from their respective jacks - do both ends. Using an ohmmeter set on continuity, ring out the RCA jack grounds (to ground) on the amplifiers. If they show continuity, do the same on the deck. This will tell you which end is the "funky" one. If neither end shows continuity, THAT is why touching a wire between ground and the shield kills the whine. Any resistance readings you receive SHOULD be less than one ohm. With a partner, check that resistance (from the RCA jacks) to the battery ground. Also check the resistance from the alternator housing to battery ground. It should effectively be the SAME resistance as the meter leads alone.

---

I'm a little fuzzy on using my ohmmeter. I'm not entirely sure what you mean by ring out the RCA grounds (to ground) on the amplifiers?

Can you explain the produce more simply?

Thanks,

-Greg

From the visible silver (or gold plated) part on the RCA jacks to the ground terminal of the amplifier or deck.

"Ringing it out" is just a term that means "test for continuity", because most continuity testers have a buzzer of some sort that "rings" while in continuity mode. When you hear the buzz, you have a low resistance electrical path between those two points in the circuit.

When testing for ground resistance, you need to know what your meter leads are adding to the circuit. Touch them together in "resistance" mode, and note the number that remains after about 5 seconds. (It should be about .1 to .2 ohms.) This is the number you must subtract from all resistance measurements from now on. This will get you much closer to the actual resistance that you are specifically trying to measure.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Thanks for the clarification. I will have to test this out next Monday as I am gone all weekend. It's going to bug me not having this resolved but nothing I can do about that for the moment.

Cheers,

-Greg

This is a very common problem.  What seems to be a very common cause in our shop is head unit preamp grounds have been damaged.  This happens when you connect an amplifier and have a bad ground connection on the amp.  OR if you turn on the stereo without a good ground to the amp.  What happens is the amplifier will try to ground through the RCA cables.  Often the small circuit traces inside the indash will open up like a fuse.  This will definitly cause engine noise.  Once you ground the amps correctly, the signal is now using the car chassis for the now damaged rca ground.  In some decks like Pioneer, they have fuses in the deck on the RCA connections that blow, Then there is seemingly NO rca output.  I have seen MANY Pioneer decks that have been "cobbled" by wrapping a wire around the rca connectors on the deck and grounding it to the chassis in an attempt to "undo" the damage.

While the stereo is playing and you hear the noise, Take a Jumper wire and temporarily connect the rca outer shield to ground.  If the noise lessens, or goes away, that is probably your issue.  You may have to try this with each rca connector, or with one rca connected at a time.

And hence why you do NOT fuse ground circuits. (As a general rule.)

Not that I mean to hijack, but some months ago there was a poster that thought there was an advantage to fusing the ground AS WELL AS the hot side. But they finally saw the light (without the sparks) and saw how this type of problem could occur - ie, a bad ground (or blown ground fuse) means alternate ground paths will be used.   
Summary - only fuse the hot side (as a general rule).

The resistance on all of the RCA's seems fine. I tested with one of the RCA's on the front speaker amp input and front speaker head unit output and it's like it "half plays". Upon ground out the head unit RCA's (the non used one's) it worked again. Or grounding out the RCA's.

Resistance between the amp and the ground was 0. I wasn't able to test voltage because my multimeter doesn't seem to be capable of it... thanks radio shack.

-Towels

I guess what I need is clear and concise instructions on how to test whether the pre-outs on the AMP or the pre-outs on my head unit are are not grounding properly.

I believe the RCA cables are good.

-Greg

I have no continuity from my RCA outer edge and the frame of the head unit leading to me to believe something went wrong and the lines are blown.

Sigh.

-Greg

wartowels wrote:

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I have no continuity from my RCA outer edge and the frame of the head unit leading to me to believe something went wrong and the lines are blown.

Sigh.

-Greg

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Just as I suspected.  Your amps must have tried to ground through your RCA's.  This will be a problem in the headunit at this point.  You can get by by grounding the rca sheilds on the deck to the chassis of the radio, But the radio should be looked at for a proper repair.

Agreed. I'm going to call Kenwood tomorrow, they deck is under warranty until June 19th! So there's still time!

-Greg

Well Kenwood said they would fix it, but that it would take 2-4 weeks. =(

Wait 2-4 weeks or cave in an make a ghetto fix.

I was thinking the best ghetto fix I could do would be a large ring terminal around the RCA with a small 3amp fuse attached to the back of the deck...

-Greg

if you are "handy" you could take it apart, I mean ALL THE WAY apart :) and look at the bottom of the circuit board near the RCA connectors.  It may have a burnt open circut trace.  This can be repaired if you scratch the green coating off the burnt trace and solder a single strand (one hair) from a speaker wire across the break.  Kenwood may void the warraty if you do this, but it is probably the same fix they would do for you!

i am an idiot wrote:

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https://bcae1.com/images/rca/temporaryrcashieldrepair.html

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DON'T OPEN IT!!! Try the above first... Solder to the RCA shield on the CABLE, not the deck! :)

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."